The 'receptor' molecule specific for LH-hCG will be isolated from bovine corpora lutea homogenates by separation of plasma membranes fraction by sucrose density gradient centrifugation. The plasma membranes will be solubilized and purified on a column of Sepharose 4B followed by affinity chromatography using hCG and LH coupled to cyanogen bromide-activated Sepharose beads. The products during purification will be monitored for purity by assay for specific binding using ammonium acetate-ethanol or polyethylene glycol, by electron microscopy, and by analytical ultracentrifugation. The fractions will be further purified by ion-exchange chromatography, electrophoresis and other suitable means of protein purification, to isolate the LH-hCG receptor. The receptor will be studied for its physiocochemical properties such as sedimentation rate, molecular weight, disc electrophoretic patterns on polyacrylamide gel with and without SDS, the dissociation behaviour with denaturing agents, specificity of binding, and stability. The conditions required for the optimum specific binding, such as, pH, cofactors and lipid requirements, etc. will be studied. The purified receptor will be analyzed for amino acid, carbohydrate and lipid compositions. The hormone-banding parameters will be studied using enzymatically or chemically modified receptor and hormone. Antibodies to the isolated receptor will be raised in rabbits and tested for specificty. In vitro studies will be undertaken to characterize receptor-mediated target cell response to hormone action. These experiments should lead to a better understanding of the role of the LH-hCG receptor at the molecular and cellular levels.